Roses are flowers that almost everyone likes, whether they are given to you as a gesture of love or whether you want to appreciate it from a distance. However, most of the time, we don’t notice other parts of the rose plant or their fallen leaves in our garden.
Have you ever noticed a black spots on rose leaves? You probably saw it recently, which brought you here to this article. Suppose you have not noticed a black spot on rose leaves, not to worry. We got you covered with what it is, the symptoms, how to prevent black spot, and how to treat it.
What Is It?
The black spot will look like nothing but circular spots on the leaves of roses. If left unchecked, the black spots can merge. The fungal disease can infect young canes too.
The black spot that you see on a leaf of a rose plant is nothing other than the fungus diplocarpon rosae. This disease is widespread among rose plants. The fungus does not kill the rose plant straight away. However, over some time, the falling of leaves can cause the rose plant to get weak.
The infected leaves cause the other leaves to get more vulnerable to secondary infections like other fungal diseases, adverse environmental conditions, and winter injuries.
What Causes It?
The fungus causes the rose black spot. It infects roses through tiny spores.
The black spots produce spores. These spores spread to new leaves through wind, water, gardening tools, and even insects. The symptoms appear some days after the leaves are infected.
The fungal diseases survive pretty well on fallen leaves or infected canes until spring. That is when spores are produced and get spread. The spores get splashed over the lower leaves first before the upper ones.
As there is a continuous cycle of infection during the growing season, the black spot tends to spread quickly, and it can become destructive to the leaves.
How To Identify?
Here, we will describe the signs and symptoms for you to look out to know if the fungus has attacked the rose plant.
The black spots usually measure one-tenth to around one-half inches in diameter. They start on the upper leaf surface of the rose leaves. The parts of the leaves right next to the black spots become yellow. The leaves drop off prematurely. They start towards the lower part of the plant and start spreading upwards.
Raised blotches that are purple-red develop on the first-year canes wood that is immature. These spots turn blackened and get blistered later on.
Treat And Prevent
Let’s talk about how you can prevent and treat when the fungus diplocarpon rosae affect your rose plant leaves. It is essential to know this as the disease can affect your garden at any time, and you need to know what to do to control its spread.
1. The Removal Of Diseased Rose Leaves From The Garden.
When you see the diseased yellow leaves with a black spot growing on the plant, remove and dispose them off as quickly as you can. Rose plant leaves that are dead and fallen on the ground also need to be thrown away. Prune canes are diseased before growth begins in the spring season.
2. Keep The Foliage Conditions Dry As Much As Possible.
The spores of the fungus require a wet surface for growing and causing infection of the leaves. This is why it is necessary to maintain the foliage as dry as you can. You can water the rose plant earlier in the day so that it is dehydrated by nighttime.
When you prune the rose plant, it allows for good air circulation.
3. Using A Fungicide Spray For Prevention Of Black Spot
Fungicides can be used to protect the leaves of the roses. Fungicides cannot remove the black spot caused by the fungus but can prevent the black spot from occurring. The pesticides used include Daconil, Captan, Copper, Maancozeb, Ziram, and Sulfur.
Many other products can be used that are known as rose dust. The majority of fungicides have to be applied every 7 to 14 days to prevent black spot.
Any fungicide needs to be applied again after it rains or overhead watering more than 1/4th inch.
4. Moving The Plants That Grow Roses
One way to limit the disease is by moving the infected leaves plants to an area where the plants will receive maximum sunlight. Moving them will help the foliage to remain dry most of the time and prevent infection. It is a great way to avoid a black spot on the leaf.
5. Replanting With More Varieties That Are Disease Tolerant
Many varieties are susceptible to getting infected with the disease, and many are resistant. It can take a while for you to understand these varieties. However, it is an intelligent choice to make early on to control the spread of the disease in roses.
You can use this replanting technique by avoiding very susceptible cultivars such as copper and yellow colored roses. The following roses were highly resistant: Coronado, Fortyniner, Carefree Beauty, Bonica, Simplicity, and Grand Opera.
You can find out about other resistant roses at your nursery.
It is essential to observe the rose flower and the leaves as well. The black spot on the rose’s leaf in your garden can affect another significant part of your garden. You need to catch it and control it early. The earlier you start the treatment, the better it is for the rose leaf.
Good air circulation, reducing watering, using a spray fungicide, and many more methods have been discussed in the article to help with the control and treatment of the black spot on roses. It is easier to prevent the black spot than getting into its treatment when it comes to roses.
We hope this article has helped you with learning all about the black spot on the plants of roses and the damage they can do to the garden.
James Fields is the founder of Gardener to Farmer. His passion for gardening goes back to his childhood days when he would visit his grandfather during the holidays and help him with the plants in the backyard. This has now translated to creating a dependable resource for gardening.